Three ships hit by whalers: Sea Shepherd

Three Sea Shepherd ships have been rammed by Japan's whaling fleet while it was attempting to refuel in Australian Antarctic Territory waters, the conservation group says.

Sea Shepherd founder Paul Watson says the Nisshin Maru has hit the Steve Irwin, the Bob Barker and the Sam Simon, which were attempting to stop the Japanese fleet "illegally" refuelling.

Captain Watson said the Nisshin Maru also collided with the Korean-owned tanker Sun Laurel, which appeared to be leaving the area.

The Bob Barker was badly damaged, taking water in its engine room and losing power, but is under way again, he said.

There were no injuries among its 38 crew.

"It's extremely irresponsible and reckless for them to be taking these kind of manoeuvres around an oil tanker, especially in the Antarctic treaty zone," Captain Watson told AAP.

"The Nisshin Maru just came in, bullied their way through, and hit the Steve Irwin twice on the stern ... and hit the Bob Barker multiple times, pushing it into the side of the tanker.

"It then continued to hit it with stun guns and water cannons and did severe damage."

Captain Watson said the Japanese ship backed off when a mayday call was issued but the Sam Simon had then been hit.

"We actually had the situation of the Japanese ship on their loudspeakers telling the Sam Simon to leave the Australian Antarctic Territory, that's an Australian flagged ship, and they said so by order of the government of Japan," Captain Watson said.

The alleged incidents immediately sparked calls for Australia to police its territorial waters, most loudly from former Greens leader Bob Brown.

"This is a gross breach of international law by the Japanese," Dr Brown, who is a director of Sea Shepherd Australia, told reporters in Melbourne.

"I'm calling the Australian government to dispatch naval vessels now - not just to film the slaughter of the whales by the Antarctic fleet but to restore international law."

Dr Brown said the incident was the worst since the sinking of the Ady Gil in 2010.

Federal Environment Minister Tony Burke said he was aware of reports of the incident.

"We are still confirming the reports," he said in a statement.

"The government condemns so-called 'scientific' whaling in all waters and we urge everyone in the ocean to observe safety at sea."

The Japanese Institute of Cetacean Research wouldn't comment when contacted by AAP but last week said the Bob Barker had tried to sabotage the Nisshin Maru and Yushin Maru No.2 as they tried to transfer a whale between the two ships.

"The Institute of Cetacean research strongly condemns the SS (Sea Shepherd) and its imprudent and violent actions perpetrated against the integrity and safety of Japan's whale research vessels and crews," a February 15 statement read.

The confrontation comes after the US Supreme Court this month upheld an injunction ordering Sea Shepherd to keep away from Japanese whaling ships in the Southern Ocean.

Opposition spokesman on the environment Greg Hunt said it was lucky that the incident did not result in serious injury, loss of life or environmental damage.

He accused the federal government of ignoring warnings about the confrontation.

Mr Hunt says if elected the coalition will send a customs vessel to the Southern Ocean to send clear message that Australians do not support whaling.

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